Should You Worry? Petrol in a Diesel Car in Warden
Likely less than you already are — as long as no one has started it. Everyone around Warden begins with "have I wrecked it?", and the honest answer is generally no: petrol resting in the tank of any diesel stays harmless till priming, cranking or driving pulls it into the fuel system. Petrol in Diesel is who to phone, with the engine kept off, so it stays that way. The remainder of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
Your engine and petrol in a diesel: what goes on
On its way through a motor, diesel has two jobs. Before it combusts, it lubricates — and then it combusts. Designed to very fine gaps, the injectors and the pump rely on the diesel flowing through them to stop their surfaces wearing against one another.
Of those two jobs, petrol handles the first poorly and the second never. A pump working on a petrol mixture is wearing itself out, since petrol is runnier than diesel and takes away the lubrication your fuel system relies on. Petrol is also made to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where the clattering starts.
The shape of the trouble is clear when you put those together. It is circulation that causes the harm, not contact. Petrol in the tank is a fuel problem. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors further along, which is why a pump that has worked on that petrol is where a mechanical fault starts.
How bad is petrol in a diesel? Four situations our technicians see in Warden
Filled up, and never started: no case is better. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol kept in your tank alone, it's drained and flushed right where it stands, and nothing more is needed.
Your ignition turned on, or a short start. Petrol has left your tank and reached the fuel filter and the lines, since the system has been bled. Still generally simple: drain, flush, and the fuel filter dealt with.
Your pump now spent a couple of miles on thinned fuel — that is what driving the vehicle meant. The work is that tank, the lines, the fuel filter and fresh fuel through the entire circuit, and how hard the car was driven counts as much as how far. On the school run to Kington Primary School, the miles is short. A run as far as Hereford, under 25 miles away, is a very different task. So is any distance on the M50, under 50 miles from Warden, where your engine has been labouring hard the whole time.
Knocking, a ragged idle, smoke, a throttle gone soft: driven till it complained. That is the engine telling you its fuel no longer is acting like diesel. Pull up wherever you are — the verge on Castle Road, a lay-by, a side street — and leave it there. The drain and flush-through still go first, and they sort it out: if a car is pulled over early, lasting damage is very unusual.
Myths Warden motorists hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A fuller tank of the same mixture is all you get, because topping up takes out nothing. The assumption behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the reverse is true. Myth: "A newer diesel can cope with a bit of petrol." A newer diesel sends its fuel through finer parts at higher pressure, which makes the lubrication count more, not less.
"It starts, it drives, so no harm done" — the myth that catches most motorists than any other. The motorist of a petrol engine fed diesel normally stops, since it will not run, and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile the pump grinds. Running is not the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different fault. None of what petrol thinned gets put back by it — and later, your tank still holds the petrol.
If the motor has been run, part of the petrol is in the fuel filter and the lines, not your tank — and your next start pulls it right back through your pump. So the myth "drain the tank yourself and you are sorted" doesn't hold. And, a can of petrol drained by the roadside is truly risky.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly will not fit a petrol car, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake easy, and only in one direction.
Routine and the vehicle falling out of step is when it occurs. Any motor that is new to you — a hire car, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps arranged differently. Fuelling up in a rush en route to Knighton, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is precisely the moment it occurs. With rain, a call coming in, or a car full of children to deal with, the hand just does what it always has.
Warden drivers: how to prevent petrol in a diesel next time
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Check the pump's label; the colour is only a hint.
- In a vehicle you do not know, look inside the flap over your filler or at the cap before your first fill: many motors state the fuel type there.
- Mark your key. In a house with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- Before the nozzle leaves the pump the first time you fuel a hired or new vehicle, say "diesel" out loud. Daft, perhaps, yet it works.
- Tuck the phone away. This is an easy mistake to make while you are thinking about something else.
- Add-on devices exist for vehicles without one, and some diesels are built with a filler that won't accept a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Stop as soon as you notice. Less petrol in that tank makes a thinner mixture. It doesn't change what to do next, which is still not to fire it up.
Put petrol in a diesel in Warden already?
In that case, there's only a short order of things. Starting it is out, and so is turning on the ignition. The attendants at the forecourt — whether at Pace itself or wherever you filled up — will usually help roll it clear of the petrol pump if you ask. Phone 0333 366 0103 next, with three answers — the fuel, the rough amount, and whether it has run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a different issue — Warden has a page just for it.
One petrol in a diesel job around Warden costs more than another. Why?
An honest single price doesn't exist here: four situations, four separate tasks. The scenario itself does most of the work of moving the cost. Where the car is counts too, and whether a van can safely reach it, after the proportion of petrol to what your tank holds.
Three questions come first, before any quote, rather than after — what went in, how much, has it run — and that is the reason. A range becomes a straight figure when those answers are in.
About Warden
Warden is a suburban area situated on the riverside in Powys, Wales, with a mix of detached housing and a population of around 1564 residents. Warden sits at an elevation of 163 metres, close to the English border and near the towns of Presteigne and Stapleton. Warden is located near the city of Hereford, which is approximately 19 miles away, and is part of a wider region that includes the town of Slough, although the latter is not in close proximity. Warden's riverside setting provides a distinctive character to the area.
Warden and Powys: where our fuel drain cover reaches
The teams answering petrol in diesel calls around Warden, in the LD postcode area, also work the places around it, Presteigne, Slough and Stapleton among them. A forecourt, a supermarket car park, a lay-by or your own drive are all places we drain, and your vehicle doesn't need to come to us.
In Warden and still at the pump?
Nothing beats it: that is where you are. Keep it off. Ring.